{section: Converting Sock}
Sock is not only used by TCP/UDP connection but also used by Unix domain socket (AF_UNIX). Basically, Sock can only create TCP or UDP socket internally but SharedEndPoint and SharedPortClient creates Unix domain socket and calls Sock::assign() to pass the descriptor.

I guess this is broken abstraction since Sock has IP related functions such as peer_addr() or peer_port() which are not available to Unix domain socket.

It seems assign() is only used by these Shared* thing. So maybe we could end up with refactoring it.

This makes conversion complicated. I hope to get 'clean' code.

{section: What is it?}
What is CEDAR??
TCP_FORWARDING_HOST ?